C++ DominatorTreeWrapperPass类代码示例

bool StackProtector::runOnFunction(Function &Fn) {
  F = &Fn;
  M = F->getParent();
  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : nullptr;
  TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();
  HasPrologue = false;
  HasIRCheck = false;

  Attribute Attr = Fn.getFnAttribute("stack-protector-buffer-size");
  if (Attr.isStringAttribute() &&
      Attr.getValueAsString().getAsInteger(10, SSPBufferSize))
    return false; // Invalid integer string

  if (!RequiresStackProtector())
    return false;

  // TODO(etienneb): Functions with funclets are not correctly supported now.
  // Do nothing if this is funclet-based personality.
  if (Fn.hasPersonalityFn()) {
    EHPersonality Personality = classifyEHPersonality(Fn.getPersonalityFn());
    if (isFuncletEHPersonality(Personality))
      return false;
  }

  ++NumFunProtected;
  return InsertStackProtectors();
}

bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) {
  if (skipOptnoneFunction(L))
    return false;

  LI = &getAnalysis<LoopInfo>();
  LPM = &LPM_Ref;
  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : 0;
  currentLoop = L;
  Function *F = currentLoop->getHeader()->getParent();
  bool Changed = false;
  do {
    assert(currentLoop->isLCSSAForm(*DT));
    redoLoop = false;
    Changed |= processCurrentLoop();
  } while(redoLoop);

  if (Changed) {
    // FIXME: Reconstruct dom info, because it is not preserved properly.
    if (DT)
      DT->recalculate(*F);
  }
  return Changed;
}

void LowerEmAsyncify::FindContextVariables(AsyncCallEntry & Entry) {
  BasicBlock *AfterCallBlock = Entry.AfterCallBlock;

  Function & F = *AfterCallBlock->getParent();

  // Create a new entry block as if in the callback function
  // theck check variables that no longer properly dominate their uses
  BasicBlock *EntryBlock = BasicBlock::Create(TheModule->getContext(), "", &F, &F.getEntryBlock());
  BranchInst::Create(AfterCallBlock, EntryBlock);

  DominatorTreeWrapperPass DTW;
  DTW.runOnFunction(F);
  DominatorTree& DT = DTW.getDomTree();

  // These blocks may be using some values defined at or before AsyncCallBlock
  BasicBlockSet Ramifications = FindReachableBlocksFrom(AfterCallBlock); 

  SmallPtrSet<Value*, 256> ContextVariables;
  Values Pending;

  // Examine the instructions, find all variables that we need to store in the context
  for (BasicBlockSet::iterator RI = Ramifications.begin(), RE = Ramifications.end(); RI != RE; ++RI) {
    for (BasicBlock::iterator I = (*RI)->begin(), E = (*RI)->end(); I != E; ++I) {
      for (unsigned i = 0, NumOperands = I->getNumOperands(); i < NumOperands; ++i) {
        Value *O = I->getOperand(i);
        if (Instruction *Inst = dyn_cast<Instruction>(O)) {
          if (Inst == Entry.AsyncCallInst) continue; // for the original async call, we will load directly from async return value
          if (ContextVariables.count(Inst) != 0)  continue; // already examined 

          if (!DT.dominates(Inst, I->getOperandUse(i))) {
            // `I` is using `Inst`, yet `Inst` does not dominate `I` if we arrive directly at AfterCallBlock
            // so we need to save `Inst` in the context
            ContextVariables.insert(Inst);
            Pending.push_back(Inst);
          }
        } else if (Argument *Arg = dyn_cast<Argument>(O)) {
          // count() should be as fast/slow as insert, so just insert here 
          ContextVariables.insert(Arg);
        }
      }
    }
  }

  // restore F
  EntryBlock->eraseFromParent();  

  Entry.ContextVariables.clear();
  Entry.ContextVariables.reserve(ContextVariables.size());
  for (SmallPtrSet<Value*, 256>::iterator I = ContextVariables.begin(), E = ContextVariables.end(); I != E; ++I) {
    Entry.ContextVariables.push_back(*I);
  }
}

bool LazyValueInfo::runOnFunction(Function &F) {
  AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
  const DataLayout &DL = F.getParent()->getDataLayout();

  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : nullptr;

  TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();

  if (PImpl)
    getCache(PImpl, AC, &DL, DT).clear();

  // Fully lazy.
  return false;
}

bool StackProtector::runOnFunction(Function &Fn) {
  F = &Fn;
  M = F->getParent();
  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : nullptr;
  TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();

  Attribute Attr = Fn.getFnAttribute("stack-protector-buffer-size");
  if (Attr.isStringAttribute() &&
      Attr.getValueAsString().getAsInteger(10, SSPBufferSize))
      return false; // Invalid integer string

  if (!RequiresStackProtector())
    return false;

  ++NumFunProtected;
  return InsertStackProtectors();
}

bool StackProtector::runOnFunction(Function &Fn) {
  F = &Fn;
  M = F->getParent();
  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : 0;
  TLI = TM->getTargetLowering();

  if (!RequiresStackProtector())
    return false;

  Attribute Attr = Fn.getAttributes().getAttribute(
      AttributeSet::FunctionIndex, "stack-protector-buffer-size");
  if (Attr.isStringAttribute())
    Attr.getValueAsString().getAsInteger(10, SSPBufferSize);

  ++NumFunProtected;
  return InsertStackProtectors();
}

void doMemToReg(Function &F) {
  std::vector<AllocaInst*> Allocas;

  BasicBlock &BB = F.getEntryBlock();  // Get the entry node for the function

  DominatorTreeWrapperPass DTW;
  DTW.runOnFunction(F);
  DominatorTree& DT = DTW.getDomTree();

  while (1) {
    Allocas.clear();

    // Find allocas that are safe to promote, by looking at all instructions in
    // the entry node
    for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
      if (AllocaInst *AI = dyn_cast<AllocaInst>(I))       // Is it an alloca?
        if (isAllocaPromotable(AI))
          Allocas.push_back(AI);

    if (Allocas.empty()) break;

    PromoteMemToReg(Allocas, DT);
  }
}

bool LoopInstSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
  if (skipOptnoneFunction(L))
    return false;

  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
  LoopInfo *LI = &getAnalysis<LoopInfo>();
  DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
  const DataLayout *DL = DLP ? &DLP->getDataLayout() : nullptr;
  const TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfo>();
  AssumptionTracker *AT = &getAnalysis<AssumptionTracker>();

  SmallVector<BasicBlock*, 8> ExitBlocks;
  L->getUniqueExitBlocks(ExitBlocks);
  array_pod_sort(ExitBlocks.begin(), ExitBlocks.end());

  SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;

  // The bit we are stealing from the pointer represents whether this basic
  // block is the header of a subloop, in which case we only process its phis.
  typedef PointerIntPair<BasicBlock*, 1> WorklistItem;
  SmallVector<WorklistItem, 16> VisitStack;
  SmallPtrSet<BasicBlock*, 32> Visited;

  bool Changed = false;
  bool LocalChanged;
  do {
    LocalChanged = false;

    VisitStack.clear();
    Visited.clear();

    VisitStack.push_back(WorklistItem(L->getHeader(), false));

    while (!VisitStack.empty()) {
      WorklistItem Item = VisitStack.pop_back_val();
      BasicBlock *BB = Item.getPointer();
      bool IsSubloopHeader = Item.getInt();

      // Simplify instructions in the current basic block.
      for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
        Instruction *I = BI++;

        // The first time through the loop ToSimplify is empty and we try to
        // simplify all instructions. On later iterations ToSimplify is not
        // empty and we only bother simplifying instructions that are in it.
        if (!ToSimplify->empty() && !ToSimplify->count(I))
          continue;

        // Don't bother simplifying unused instructions.
        if (!I->use_empty()) {
          Value *V = SimplifyInstruction(I, DL, TLI, DT, AT);
          if (V && LI->replacementPreservesLCSSAForm(I, V)) {
            // Mark all uses for resimplification next time round the loop.
            for (User *U : I->users())
              Next->insert(cast<Instruction>(U));

            I->replaceAllUsesWith(V);
            LocalChanged = true;
            ++NumSimplified;
          }
        }
        bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
        if (res) {
          // RecursivelyDeleteTriviallyDeadInstruction can remove
          // more than one instruction, so simply incrementing the
          // iterator does not work. When instructions get deleted
          // re-iterate instead.
          BI = BB->begin(); BE = BB->end();
          LocalChanged |= res;
        }

        if (IsSubloopHeader && !isa<PHINode>(I))
          break;
      }

      // Add all successors to the worklist, except for loop exit blocks and the
      // bodies of subloops. We visit the headers of loops so that we can process
      // their phis, but we contract the rest of the subloop body and only follow
      // edges leading back to the original loop.
      for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
           ++SI) {
        BasicBlock *SuccBB = *SI;
        if (!Visited.insert(SuccBB).second)
          continue;

        const Loop *SuccLoop = LI->getLoopFor(SuccBB);
        if (SuccLoop && SuccLoop->getHeader() == SuccBB
                     && L->contains(SuccLoop)) {
          VisitStack.push_back(WorklistItem(SuccBB, true));

          SmallVector<BasicBlock*, 8> SubLoopExitBlocks;
          SuccLoop->getExitBlocks(SubLoopExitBlocks);

          for (unsigned i = 0; i < SubLoopExitBlocks.size(); ++i) {
            BasicBlock *ExitBB = SubLoopExitBlocks[i];
            if (LI->getLoopFor(ExitBB) == L && Visited.insert(ExitBB).second)
              VisitStack.push_back(WorklistItem(ExitBB, false));
          }
//.........这里部分代码省略.........

//.........这里部分代码省略.........
   
    // To save space, for each async call in the callback function, we just ignore the sync case, and leave it to the scheduler
    // TODO need an option for this
    {
      for (std::vector<AsyncCallEntry>::iterator EI = AsyncCallEntries.begin(), EE = AsyncCallEntries.end();  EI != EE; ++EI) {
        AsyncCallEntry & CurEntry = *EI;
        Instruction *MappedAsyncCallInst = cast<Instruction>(VMap[CurEntry.AsyncCallInst]);
        BasicBlock *MappedAsyncCallBlock = MappedAsyncCallInst->getParent();
        BasicBlock *MappedAfterCallBlock = cast<BasicBlock>(VMap[CurEntry.AfterCallBlock]);

        // for the sync case of the call, go to NewBlock (instead of MappedAfterCallBlock)
        BasicBlock *NewBlock = BasicBlock::Create(TheModule->getContext(), "", CurCallbackFunc, MappedAfterCallBlock);
        MappedAsyncCallBlock->getTerminator()->setSuccessor(1, NewBlock);
        // store the return value
        if (!MappedAsyncCallInst->use_empty()) {
          CallInst *RawRetValAddr = CallInst::Create(GetAsyncReturnValueAddrFunction, "", NewBlock);
          BitCastInst *RetValAddr = new BitCastInst(RawRetValAddr, MappedAsyncCallInst->getType()->getPointerTo(), "AsyncRetValAddr", NewBlock);
          new StoreInst(MappedAsyncCallInst, RetValAddr, NewBlock);
        }
        // tell the scheduler that we want to keep the current async stack frame
        CallInst::Create(DoNotUnwindAsyncFunction, "", NewBlock);
        // finally we go to the SaveAsyncCtxBlock, to register the callbac, save the local variables and leave
        BasicBlock *MappedSaveAsyncCtxBlock = cast<BasicBlock>(VMap[CurEntry.SaveAsyncCtxBlock]);
        BranchInst::Create(MappedSaveAsyncCtxBlock, NewBlock);
      }
    }

    std::vector<AllocaInst*> ToPromote;
    // applying loaded variables in the entry block
    {
      BasicBlockSet ReachableBlocks = FindReachableBlocksFrom(ResumeBlock);
      for (size_t i = 0; i < CurEntry.ContextVariables.size(); ++i) {
        Value *OrigVar = CurEntry.ContextVariables[i];
        if (isa<Argument>(OrigVar)) continue; // already processed
        Value *CurVar = VMap[OrigVar];
        assert(CurVar != MappedAsyncCall);
        if (Instruction *Inst = dyn_cast<Instruction>(CurVar)) {
          if (ReachableBlocks.count(Inst->getParent())) {
            // Inst could be either defined or loaded from the async context
            // Do the dirty works in memory
            // TODO: might need to check the safety first
            // TODO: can we create phi directly?
            AllocaInst *Addr = DemoteRegToStack(*Inst, false);
            new StoreInst(LoadedAsyncVars[i], Addr, EntryBlock);
            ToPromote.push_back(Addr);
          } else {
            // The parent block is not reachable, which means there is no confliction
            // it's safe to replace Inst with the loaded value
            assert(Inst != LoadedAsyncVars[i]); // this should only happen when OrigVar is an Argument
            Inst->replaceAllUsesWith(LoadedAsyncVars[i]); 
          }
        }
      }
    }

    // resolve the return value of the previous async function
    // it could be the value just loaded from the global area
    // or directly returned by the function (in its sync case)
    if (!CurEntry.AsyncCallInst->use_empty()) {
      // load the async return value
      CallInst *RawRetValAddr = CallInst::Create(GetAsyncReturnValueAddrFunction, "", EntryBlock);
      BitCastInst *RetValAddr = new BitCastInst(RawRetValAddr, MappedAsyncCall->getType()->getPointerTo(), "AsyncRetValAddr", EntryBlock);
      LoadInst *RetVal = new LoadInst(RetValAddr, "AsyncRetVal", EntryBlock);

      AllocaInst *Addr = DemoteRegToStack(*MappedAsyncCall, false);
      new StoreInst(RetVal, Addr, EntryBlock);
      ToPromote.push_back(Addr);
    }

    // TODO remove unreachable blocks before creating phi
   
    // We go right to ResumeBlock from the EntryBlock
    BranchInst::Create(ResumeBlock, EntryBlock);
   
    /*
     * Creating phi's
     * Normal stack frames and async stack frames are interleaving with each other.
     * In a callback function, if we call an async function, we might need to realloc the async ctx.
     * at this point we don't want anything stored after the ctx, 
     * such that we can free and extend the ctx by simply update STACKTOP.
     * Therefore we don't want any alloca's in callback functions.
     *
     */
    if (!ToPromote.empty()) {
      DominatorTreeWrapperPass DTW;
      DTW.runOnFunction(*CurCallbackFunc);
      PromoteMemToReg(ToPromote, DTW.getDomTree());
    }

    removeUnreachableBlocks(*CurCallbackFunc);
  }

  // Pass 4
  // Here are modifications to the original function, which we won't want to be cloned into the callback functions
  for (std::vector<AsyncCallEntry>::iterator EI = AsyncCallEntries.begin(), EE = AsyncCallEntries.end();  EI != EE; ++EI) {
    AsyncCallEntry & CurEntry = *EI;
    // remove the frame if no async functinon has been called
    CallInst::Create(FreeAsyncCtxFunction, CurEntry.AllocAsyncCtxInst, "", CurEntry.AfterCallBlock->getFirstNonPHI());
  }
}

/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge.  This will update DominatorTree information if it
/// is available, thus calling this pass will not invalidate either of them.
/// This returns the new block if the edge was split, null otherwise.
///
/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
/// specified successor will be merged into the same critical edge block.
/// This is most commonly interesting with switch instructions, which may
/// have many edges to any one destination.  This ensures that all edges to that
/// dest go to one block instead of each going to a different block, but isn't
/// the standard definition of a "critical edge".
///
/// It is invalid to call this function on a critical edge that starts at an
/// IndirectBrInst.  Splitting these edges will almost always create an invalid
/// program because the address of the new block won't be the one that is jumped
/// to.
///
BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
                                    Pass *P, bool MergeIdenticalEdges,
                                    bool DontDeleteUselessPhis,
                                    bool SplitLandingPads) {
    if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0;

    assert(!isa<IndirectBrInst>(TI) &&
           "Cannot split critical edge from IndirectBrInst");

    BasicBlock *TIBB = TI->getParent();
    BasicBlock *DestBB = TI->getSuccessor(SuccNum);

    // Splitting the critical edge to a landing pad block is non-trivial. Don't do
    // it in this generic function.
    if (DestBB->isLandingPad()) return 0;

    // Create a new basic block, linking it into the CFG.
    BasicBlock *NewBB = BasicBlock::Create(TI->getContext(),
                                           TIBB->getName() + "." + DestBB->getName() + "_crit_edge");
    // Create our unconditional branch.
    BranchInst *NewBI = BranchInst::Create(DestBB, NewBB);
    NewBI->setDebugLoc(TI->getDebugLoc());

    // Branch to the new block, breaking the edge.
    TI->setSuccessor(SuccNum, NewBB);

    // Insert the block into the function... right after the block TI lives in.
    Function &F = *TIBB->getParent();
    Function::iterator FBBI = TIBB;
    F.getBasicBlockList().insert(++FBBI, NewBB);

    // If there are any PHI nodes in DestBB, we need to update them so that they
    // merge incoming values from NewBB instead of from TIBB.
    {
        unsigned BBIdx = 0;
        for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
            // We no longer enter through TIBB, now we come in through NewBB.
            // Revector exactly one entry in the PHI node that used to come from
            // TIBB to come from NewBB.
            PHINode *PN = cast<PHINode>(I);

            // Reuse the previous value of BBIdx if it lines up.  In cases where we
            // have multiple phi nodes with *lots* of predecessors, this is a speed
            // win because we don't have to scan the PHI looking for TIBB.  This
            // happens because the BB list of PHI nodes are usually in the same
            // order.
            if (PN->getIncomingBlock(BBIdx) != TIBB)
                BBIdx = PN->getBasicBlockIndex(TIBB);
            PN->setIncomingBlock(BBIdx, NewBB);
        }
    }

    // If there are any other edges from TIBB to DestBB, update those to go
    // through the split block, making those edges non-critical as well (and
    // reducing the number of phi entries in the DestBB if relevant).
    if (MergeIdenticalEdges) {
        for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) {
            if (TI->getSuccessor(i) != DestBB) continue;

            // Remove an entry for TIBB from DestBB phi nodes.
            DestBB->removePredecessor(TIBB, DontDeleteUselessPhis);

            // We found another edge to DestBB, go to NewBB instead.
            TI->setSuccessor(i, NewBB);
        }
    }



    // If we don't have a pass object, we can't update anything...
    if (P == 0) return NewBB;

    DominatorTreeWrapperPass *DTWP =
        P->getAnalysisIfAvailable<DominatorTreeWrapperPass>();
    DominatorTree *DT = DTWP ? &DTWP->getDomTree() : 0;
    LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>();

    // If we have nothing to update, just return.
    if (DT == 0 && LI == 0)
        return NewBB;

    // Now update analysis information.  Since the only predecessor of NewBB is
    // the TIBB, TIBB clearly dominates NewBB.  TIBB usually doesn't dominate
//.........这里部分代码省略.........